Glass laminates

ABSTRACT

Glass laminates comprising two sheets of glass bonded together by a transparent plastics material have at least one of the bonded surfaces of the glass provided with a layer of aluminum phosphate. The aluminum phosphate is preferably generated from an alcoholic coating solution of a complex phosphate of aluminum, e.g., aluminum chlorophosphate ethanolate, which may be applied to the glass surface and cured by gentle heating.

United States Patent [1 1 Birchall et a1.

11 1 3,793,105 [4 1 Feb. 19, 1974 GLASS LAMINATES [75] Inventors: JamesDerek Birchall, Norley; John Edward Cassidy, Hartford; John EdwardPriddle, Welwyn; Laurence Michael Smith, Harpenden, all of England [73]Assignee: Imperial Chemical Industries Limited, London, England [22]Filed: Dec. 10,1971

[21] App]. No.: 211,856

[30] Foreign Application Priority Data Dec. 11, 1970 Great Britain59029/70 [52] US. Cl 156/106, 161/191, 161/192, 161/199, 161/204,117/54, 117/123 B [51] Int. Cl B32b 31/12, B32b 17/06 [58] Field ofSearch.... 117/54, 72 R, 123 A, 123 B; 156/99, 106; 161/41, 192, 199,191

[5 6] References Cited UNITED STATES PATENTS 3,556,890 1 1971 Buckley eta1. 156/106 3,416,950 12/1968 Schrader 117/72 x 2,702,068 2/1955SpOOner.... 117 72 x 3,464,839 9 1969 Gamble 117 123 A 2,290,193 7 1942Kirkpatrick 161/199 x Crandon et a1. 117/123 D 2,840,535 6/19583,231,440 1/1966 Mattimol et al. 156/106 X 3,388,033 6/1968 Buckley eta1. 156/106 X 2,885,417 5/1959 Heyden 117/127 3,023,337 2/1962 Repsher117/68 X FOREIGN PATENTS OR APPLICATIONS 128,992 6/1960 UIS.S.R.

OTHER PUBLICATIONS Matveev, M. A. and A. I. Rabukhin, Glass-ReinforcedPlastics, Chemical Abstracts, 31, 1090g (1961).

Primary Examiner-Charles E. Van Horn Attorney, Agent, or Firm-Cushman,Darby &

Cushman [5 7 ABSTRACT 9 Claims, No Drawings GLASS LAMINATES Thisinvention relates to glass laminates.

In the term glass we include, as well as silicate glasses for which theterm is conventionally used, transparent or translucent, substantiallyrigid sheet of plastics materials such as, for example,polymethylmethacrylate, polyvinylchloride, polystyrene or polycarbonateresin.

According to the present invention there is provided a method of makinga glass laminate by bonding together two pieces of glass by means of alayer of substantially transparent plastics material characterised inthat at least one of the glass surfaces to be bonded is pretreated byapplying to the glass surface a coating of a composition capable ofgenerating aluminum phosphate on heating and heating said coating toprovide a cured or partially cured layer of aluminum phosphate.

The present invention is also a glass laminate comprising two sheets ofglass bonded together by a substantially transparent plastics material,at least one of the bonded surfaces of the glass bearing a coating of analuminum phosphate.

By the use of an aluminum phosphate in accordance with the invention,the adhesion of the glass surface to the plastics interlayer isincreased. This effect may be used either to achieve a greater degree ofadhesion of the interlayer to the glass than when untreated glass isused, or to allow the use of bonding techniques with less criticalconditions to achieve a required degree of adhesion, so that theseconditions may be chosen with greater freedom to obtain, for example, ahigher transparency or clarity in the resulting laminate.

The composition capable of generating aluminum phosphate on heating canadvantageously be a halogencontaining complex phosphate of aluminumcontaining at least one chemically-bound molecule of a hydroxy compoundR-OH, where in R is a hydrogen atom or an organic group. Such materialsare described and claimed in U. S. Pat. application Ser. No. 42,499,filed June 1, 1970, now refiled as application Ser. No. 274,964 filedJuly 25, 1972, the disclosure of which is incorporated herein byreference.

On heating these complex phosphates at relatively low temperatures, ofthe order of 80-180 C, they decompose, evolving a hydrogen halide andthe compound R-OH, to form a hard, abrasion-resistant aluminumphosphate. As used herein, the term complex aluminum phosphate denotesthe material before decomposition by heating, while the term aluminumphosphate denotes the product obtained by decomposing the complexaluminum phosphate by heating.

The halogen in the complex aluminum phosphate is preferably chlorine.The ratio of the number of gram atoms of aluminum to the number of gramatoms of phosphorus in the complex phosphates of aluminum may vary overa wide range, for example from 1:2 to 2:1, but is preferablysubstantially 1:1 as complex phosphates of the invention having thisratio decompose at low temperatures directly to form aluminumorthophosphate having greater chemical stability and refractoriness thanaluminum phosphate formed from complex phosphates with other ratios. Itis also preferred that R is an aliphatic hydrocarbon or substitutedhydrocarbon group; in particular it is preferred that the hydroxycompound is an aliphatic alcohol containing from one to four carbonatoms, particularly methanol or ethanol. As a typical example thecomplex aluminum phosphate has an empirical formula AlPClH C 0 this canbe designated aluminum chlorophosphate ethanolate, but it is to beunderstood that this designation in no way implies any particularmolecular structure for the compound.

The complex aluminum phosphate may be applied to the glass surface as asolution in a suitable solvent, for example water or an alcohol such asmethanol or ethanol. The aluminum phosphate produced by removing thesolvent and heating to decompose the complex aluminum phosphate forms astrongly-adherent coating that is stable to high temperatures. Preferredorganic solvents are polar solvents, especially oxygencontaining polarsolvents. Aliphatic alcohols containing up to 10 carbon atoms, esters,polyhydric alcohols, and glycol esters are especially useful, aliphaticalcohols containing from one to five carbon atoms, for example methanolor ethanol, being particularly preferred. The solvent may be a mixtureof solvents.

The solution of complex phosphate preferably contains, in solution ordispersion, a material that will control the physical nature of thesolid phase of aluminum phosphate produced from the solution. When thesolvent comprises water, it is preferred to use for this purpose acrystallisation stabiliser, for example, finely divided silica oralumina, or a nucleation activator or catalyst, for example dibutylperoxide, or calcium, magnesium or sodium chloride. When the solution ofthe complex phosphate is non-aqueous, for example, when the solvent isethanol, it is preferred to use a boric acid ester or ether or a silicicacid ester or ether, for example methylborate, trimethoxyboroxine orethylsilicate, to suppress the crystallisation of aluminum phosphate.

In another method of preparing a suitable coating composition capable ofyielding an aluminum phosphate on heating, aluminum phosphate isdissolved or dispersed in hydrochloric, sulphuric,.oxalic or .citricacid or a compatible mixture of two or more such acids. Aluminumorthophosphate, for example may be used with hydrochloric acid at. molarratios varying between 1:0.1 and 1:10, preferably between 1:0.25 and1:10. Solutions obtained may optionally be diluted with water and/or analcohol for example methanol or ethanol before use as a coatingcomposition. It is preferred to dilute the solutions, if required,immediately before use because the dissolved phosphates are prone toprecipitate from dilute solutions on prolonged storage.

A solution of aluminum phosphate in hydrochloric acid may be for thepurposes of this invention made by dissolving aluminum chloride inphosphoric acid.

The coating may be applied to the glass surface by brushing,roller-coating, spraying, flowing, or by any. other convenient method.The coating is cured by heating, which serves both to remove solvent, ifpresent, and to generate a strongly adherent layer of aluminum phosphateon the surface. Heating of the phosphate coating is effected by anyconvenient means, for example 'by passing the coated glass through anair oven maintained at the required temperature. The duration of heatingis preferably at least 10 minutes. The form of aluminum phosphateproduced will depend, amongst other things, upon the temperature towhich the coating-is heated, and although a temperature of at least C isnormally sufficient to form a coat of aluminum phosphate, the coating ispreferably heated to a temperature in excess of 100 C.

The thickness of the cured aluminum phosphate layer is preferably lessthan microns, and when maximum transparency is required, is preferablyless than 3 microns. Coatings of thickness greater than about 3 micronsmay however, be used where very high transparency is not important.

Organic materials, preferably polymers, may be dissolved in thesolutions from which the coatings of this invention are produced to givecoatings comprising an organic material and aluminum phosphate. It maybe advantageous to add a suitable wetting agent to the coating solutionto assist uniform coating. Other components, for example pigments, maybe incorporated in the coating by including them in the coatingsolution.

Any of the transparent plastics materials known to be suitable for usein the production of laminated safetyglass may be used for bonding theglass laminate of the invention. Preferred materials are polyvinylbutyral and certain copolymers of ethylene, including those described inUK. Specification No. 1,166,443. The latter are copolymers of ethylenewith one or more hydroxy or epoxy aliphatic or cycloaliphatic monoestersor acrylic acid or methacrylic acid in which the aliphatic orcycloaliphatic radical consists only of carbon, hydrogen and oxygen andcontains not more than six carbon atoms, and with from zero to 55percent, by weight of the copolymer, of a further comonomer having oneethylenic double bond which is an ester of acrylic or methacrylic acidor a vinyl ester, the copolymer containing, by weight, at least 35percent of ethylene units and:

a. from 2.0 to 8.5 percent of free hydroxy groups; or

b. from 0.3 to 3.0 percent of epoxy oxygen; or c. an equivalentlyeffective amount with respect to the percentages stated in (a) and (b),of both free hydroxy groups and epoxy oxygen. 1 Other suitable ethylenecopolymers include copolymers of ethylene with acrylic acid ormethacrylic acid, and with a vinyl ester, an acrylate or a methacrylateas a third comonomer.

In a widely used process for the production of safetyglass, and suitablefor making the laminates of this invention, the sheets of glass with thefilm interlayer interposed between them are assembled in a suitable jig,and the assembly is placed in a flexible bag of plastics or rubber. Thebag is then thoroughly evacuated, and the assembly is placed in an oven,or, preferably, in an air or oil-autoclave, and heated to the desiredbonding temperature. For the ethylene copolymers preferred for use inthe method of the present invention, this is generally above 110 C,preferably between 110 and 170 C for a heating period of about to 30minutes; but higher temperatures and different time cycles may be used.The pressure of the atmosphere, when an oven is used, or the pressureapplied in the autoclave, provides for uniform contact and bondingbetween the glass sheets and the interlayer. The assembly is then cooledor allowed to cool before its removal from the bag.

Thelaminates may alternatively be made by applying heat and pressure inamechanical or hydraulic press,

with heating and cooling applied by heat transfer through the platens.The bag andautoclave method is generally much preferred for makinglaminates of high quality, particularly for making curved laminates.

The invention is of particular value when applied to the modification oftransparent safety-glass, especially that of the type used forwindscreens for motor cars and other vehicles, comprising two sheets ofsilicate glass, which may be curved or flat, with a layer of transparentbonding medium sandwiched between them. Such safety-glass must be madeto close tolerances, particularly as regards adhesion, transparency andclarity, and the manufacturing conditions are highly critical. Anywidening of the range of choice of these conditions to obtain an optimumbalance of properties is thus of value. It may also be used in theproduction of safety-glass for windows, screens or other constructionalpurposes.

The invention may also be usefully applied to the modification ofsafety-glass of the type comprising a sheet or sheets of silicate glassbonded to a sheet of a transparent or translucent, substantially rigidplastics material, or comprising two or more sheets of transparent ortranslucent, substantially rigid plastics material bonded together bythe bonding medium. Such laminates are'often used, for example forbandit-resistant and bullet-resistant glass windows for shops, showcases, banks, vehicles and the like. The substantially rigid plasticsmaterial used in such laminates is preferably an acrylic plasticsmaterial, especially polymethylmethacrylate, rigid polyvinylchloride, ora polycarbonate resin.

The invention is illustrated by the following Example in which all partsand percentages are by weight.

EXAMPLE l/8 inch thick float-glass plates (1 ft X 1 ft) were stackedtogether in pairs and each pair immersed in a 10 percent by weightsolution of aluminum chlorophosphate ethanolate in methanol contained ina polythene container (13 inch X 13 inch X 1% inch) fitted with a lidand a drain tap. The plates were immersed for. 2 minutes and drynitrogen was passed into the container as the solutionwas slowly drainedoff. The plates were heated at 120 C for 30 minutes, allowed to cool andA laminate was made up consisting of two such plates 0 having theircoated faces innermost and an interlayer of .030 inch thick ethylenecopolymer film containing 13 percent by weight methacrylic acid, 6percent vinyl acetate, 5 percent methyl-methacrylate and 76 percentethylene. This ethylene copolymer is disclosed in our co-pending DutchPatent application No. 71/09975. The laminate was placed in apolyvinyl-chloride bag, which was sealed and evacuated. The bag with itscontents was placed in an oven at C. After 40 minutes at thistemperature, the bag was removed and the laminate quench-cooled in waterat 50 C.

Laminates made according to the above process were tested for impactperformance, optical properties and together two pieces of glass bymeans of a layer of substantially transparent plastics materialcharacterised in that at least one of the glass surfaces to be bonded ispretreated by applying to the glass surface a coating of a compositioncomprising a halogen-containing complex aluminum phosphate containing atleast one chemically-bound molecule of a hydroxy compound ROH wherein Ris a hydrogen atom or an aliphatic hydrocarbon group, and heating saidcoating to at least 80 C to provide a cured or partially cured layer ofaluminum phosphate.

2. A method as claimed in claim 1 wherein the hydroxy compound in thehalogen-containing complex aluminum phosphate is an aliphatic alcoholcontaining one to carbon atoms.

3. A method as claimed in claim 2 wherein the hydroxy compound isethanol.

4. A method as claimed in claim 1 wherein the comtion of the complex ofaluminum in HCl.

2. A method as claimed in claim 1 wherein the hydroxy compound in thehalogen-containing complex aluminum phosphate is an aliphatic alcoholcontaining one to 10 carbon atoms.
 3. A method as claimed in claim 2wherein the hydroxy compound is ethanol.
 4. A method as claimed in claim1 wherein the complex aluminum phosphate contains chlorine.
 5. A methodas claimed in claim 1 wherein the complex aluminum phosphate has theempirical formula AlPClH25C8O8.
 6. A method as claimed in claim 1wherein the coating composition comprises the halogen-containing complexdissolved in an organic solvent.
 7. A method as claimed in claim 6wherein the solvent is methanol.
 8. A method as claimed in claim 1wherein the coating composition comprises the complex aluminum phosphatesolution.
 9. A process as claimed in claim 8 wherein the coatingcomposition comprises an aqueous alcoholic solution of the complex ofaluminum in HCl.